Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforward	$ 36,093	$ 20,276
Intangible assets	45	38
Accrued expense	605	508
Stock-based compensation	1,237	682
Other	126	73
Total deferred tax assets	49,553	29,196
Deferred tax liabilities
Depreciable assets	(72)	(74)
Total deferred tax liabilities	(72)	(74)
Less: Valuation allowance	(49,481)	(29,122)
Deferred tax assets, net	0	0
Federal
Deferred tax assets
Tax credits	10,859	7,260
State
Deferred tax assets
Tax credits	$ 588	$ 359